This disclosure relates in general to the field of centrifugal separators, and more particularly to a centrifuge having replaceable internal components.
Over the past several years, demand has increased for the efficient removal of contaminants from water supplies. Because of their relatively small size, many light density contaminants (e.g., microorganisms) have failed to be removed by conventional processing methods including fluid separation.
Fluid separation may include any process that captures and removes materials from a liquid stream, typically resulting in a clarified liquid having reduced contaminants and a denser stream containing removed contaminants. Further treating the denser stream in a thickening process may remove additional liquid to leave a thick, pump-able slurry mixture containing nine to approximately twelve percent solids by weight. Under certain conditions, a de-watering process may remove more water from the slurry mixture. The de-watering process may create a stackable but still moist mixture of approximately twelve to thirty percent solids by weight. In an extreme de-watering process, the resulting mixture may comprise up to forty percent solids by weight. In treating a clarified liquid, an associated clarifying process may remove suspended solid particles leaving a substantially further clarified fluid.
One type of fluid separation technique may include a membrane filtration process. Typically, a membrane filtration process removes particles from a liquid by retaining the particles in a filter of a specific size suited for a particular application. Some examples of membrane filtration processes include microfiltration, ultrafiltration, and nanofiltration. For insoluble particles, microfiltration can be used to retain and remove these particles from a liquid. Ultrafiltration may define a purification process that serves as a primary purification filter to isolate a desired solid product of a specific size. A nanofiltration process may be used in a final purification process to remove contaminants as small as microscopic bacterial cyst.
Another example of a fluid separation technique may include centrifugal separation. In centrifugal separation, a centrifuge may use centrifugal force to separate more dense contaminants from a fluid medium to leave a clarified fluid. By creating a centrifugal force several times greater than gravity, more dense contaminants separate from the fluid medium. To create centrifugal force within the centrifuge, the fluid medium is often placed within a chamber that rotates along a symmetrical axis creating the centrifugal force in a radial direction away from the symmetrical axis. More dense contaminants suspended in the fluid medium are forced against an outer wall of the rotating chamber and may pass through openings in the chamber to an outer catchment basin. The resulting clarified fluid, which is less dense, remains near the axis of rotation and may typically be removed from the chamber via a clarified fluid outlet.
One method of controlling a centrifugal separation process is to vary the centrifugal force within the chamber. To increase the centrifugal force, either the diameter of the rotating chamber and/or the rotational speed of the chamber can be increased. While increasing rotational speed of a centrifuge may increase the centrifugal force in order to remove smaller, less dense contaminants, problems may also be created by the additional centrifugal force.
Some of the problems associated with increasing centrifugal force within a chamber include burst pressure, balancing, and abrasion. Because more dense contaminants are generally forced against the outer wall or walls of the rotating chamber, burst pressure limits of materials used to form the outer wall or walls may become a critical design element of the chamber. Dynamic balancing of the rotating chamber may also become a problem when wall thickness is increased to provide a higher burst pressure design and/or when rotation speeds are increased. When centrifugal force is increased, the velocity of the more dense contaminants may increase causing any particulate matter to travel at high speeds. The high speed of the more dense particles may impart an abrasive quality when particulate matter contacts the walls of the chamber, which may eventually ablate the chamber walls.
As more dense contaminants are extracted from a fluid medium, the openings formed in the wall that allow the more dense contaminants to be expelled from the rotating chamber may become clogged with particulate matter or solids. Despite high centrifugal force, particulate matter may clog the openings and create a build up of relatively solid materials behind this xe2x80x9cclog-pointxe2x80x9d. Once an opening is clogged, the centrifuge must be stopped and the clog cleared in order for the centrifuge to be returned to service.
Another problem may exist due to the increased rotation of the chamber. As the chamber rotates around a center axis, inertia or momentum of the fluid medium being rotated may develop an inner swirling pattern within the chamber, known as a cyclonic vorticity. Because this vorticity often creates an agitation within the associated chambers, it may be desired to avoid this cyclonic vorticity effect by limiting rotational speeds.
In accordance with teachings of the present invention, disadvantages and problems associated with a centrifuge have been substantially reduced or eliminated. In one embodiment, a centrifuge for removing more dense particles or other more dense contaminants from a fluid medium may include a separation wall placed within a non-rotating sleeve to form a containment zone for the more dense particles or other more dense contaminants therebetween. The separation wall may include an inner surface, a center section, and an outer surface. The separation wall may be aligned generally parallel with an axis of rotation and rotate around the axis of rotation. One or more receptacles may be formed in the separation wall in accordance with teachings for the present invention. Each receptacle may include a respective geometry formed on the inner surface and a respective shape formed in the center section to define a void area to aid in separation of the more dense particles and other dense contaminants. The separation wall may also include an opening extending through the separation wall from the inner surface to the outer surface. This opening may transport the more dense particles and other contaminants to the containment zone.
In another embodiment of the present invention, a method of constructing a centrifuge for separating more dense particles from a fluid medium may include providing a centrifuge core disposed within a non-rotating sleeve. The centrifuge core may include a separation wall with an inner surface, a center section and an outer surface. One or more receptacles may be formed on the inner surface of the separation wall. Each receptacle may aid in separation of the more dense particles from a fluid medium. The method may include forming the centrifuge core from a plurality of generally cylindrical discs. Alternatively the centrifuge core may be formed from a plurality of generally longitudinal wedges. The method may include aligning the generally cylindrical discs or generally longitudinal wedges along an axis of rotation. The centrifuge core may rotate around this axis causing a centrifugal force to be imparted on the more dense particles to separate them from the fluid medium.
In a further embodiment of the present invention, a method of removing more dense particles from a fluid medium may include forming a centrifuge with a centrifuge core disposed within an outer non-rotating collecting sleeve. The centrifuge core may include a separation wall having at least one receptacle with an opening and a flow path extending therethrough. By rotating the centrifuge core around an axis of rotation, a centrifugal force may be created. The more dense particles may be removed through an opening in the receptacle and through the flow path to the outer non-rotating collecting sleeve. The method may include creating a cyclonic vorticity within the receptacle. The cyclonic vorticity may aid in preventing the more dense particles from clogging the opening.
One technical advantage of the present invention may include prevention of clogging of openings in a fluid separation wall. In some embodiments of the present invention, an anti-clogging projection may be placed in the opening to prevent clogging by the more dense particles. The anti-clogging projection may be formed within the inner surface of a nozzle to create a turbulent flow out of the nozzle. The turbulent flow may prevent blockage as the more dense particles exit the nozzle.
Another technical advantage of the present invention includes disrupting any cyclonic vorticity created in a void area of a receptacle. Placing an anti-vorticity projection in a receptacle may prevent formation of a cyclonic vorticity within the void area of the receptacle. Preventing this vorticity may enhance separation of the more dense particles from the fluid medium.
A further technical advantage of the present invention may include varying the velocity of separation of the more dense particles in the fluid medium. Forming steep or shallow walls on an interior of the receptacle walls may create a frictional force as the more dense particles move towards the opening. This frictional force may vary depending upon the angle or slope of the receptacle walls. By increasing the angle or slope, such as adding a steep wall, the more dense particles may move more rapidly toward the opening. This may decreases the separation effects caused the centrifugal force since less dense fluid may be carried out opening along with the more dense fluid. Providing a shallow sloped wall on the interior of the receptacle allows frictional forces to slow the speed of the particles, which permits additional removal of liquids such as water from the particles as they move more slowly along the walls of the receptacle towards the opening.
All, some or none of these technical advantages may be present in various embodiments of the present invention. Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.